This invention relates to a silver complex diffusion transfer material in which a photosensitive material and an image receptive material are combined. It relates, more particularly, to an improvement of said image receptive material.
The silver complex diffusion transfer process generally involves, as essential materials, a photosensitive material comprising a support and, provided thereon, a silver halide emulsion layer which serves as photosensitive layer, an image receptive material comprising a support and, provided thereon, an image receptive layer containing physical development nuclei, and a processing composition containing a solvent for the silver halide. The silver complex diffusion transfer process proceeds, in principle, in a manner such that upon exposure the silver halide of the exposed areas in a photosensitive layer is developed with a processing composition or a developing agent in the photosensitive material, while, at the same time, the silver halide in the unexposed areas reacts with a silver halide solvent in the processing composition, forming a soluble silver complex which diffuses into an image receptive material and deposits on the physical development nuclei in the image receptive layer, forming a silver image. This process is widely utilized in copying documents such as prints, hand-written documents, and design drawings. For such purposes the process is required to be able to reproduce the image faithfully to the original. It is important for the image receptive material to exhibit such essential properties as high optical density (both reflection and transmission densities) and good tone (blue black tone being generally preferred) of the silver image, high rate of diffusion transfer, and sufficient film strength of the image receptive layer. Above all, the optical density (both reflection and transmission densities) of silver image is a very important quality. Copies are generally required to be of high sharpness resulting from a high density of the silver image. In the case of block copy, a high density of the silver image is preferred for the faithful reproduction of the image quality (fine lines and dots).
As described above, it is not too much to state that the performance characteristics of an image receptive material depend largely upon the optical density of silver image. For this reason, research and development of an image receptive material which may afford a high density silver image are being actively in progress in the art.
In the sensitive material used in common black and white photography, the directly developed silver halide grains determine the silver image density, whereas in the silver complex diffusion transfer process, the enviromental conditions under which the soluble silver complex is developed within the image receptive layer seem also to affect greatly the silver image density.